2018-08-13 22:44:46 +00:00
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package mcfg
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2018-08-14 00:05:22 +00:00
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import (
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"context"
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"encoding/json"
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)
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2018-08-13 22:44:46 +00:00
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// ParamValue describes a value for a parameter which has been parsed by a
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// Source.
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type ParamValue struct {
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Name string
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Path []string
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Value json.RawMessage
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}
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// Source parses ParamValues out of a particular configuration source, given a
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// sorted set of possible Params to parse, and the Context from with the Params
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// were extracted.
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//
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// It's possible for Parsing to affect the Context itself, for example in the
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// case of sub-commands. For this reason Parse can return a Context, which will
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// get used for subsequent Parse commands inside, and then returned from,
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// Populate.
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//
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// Source should not return ParamValues which were not explicitly set to a value
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// by the configuration source.
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//
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// The returned []ParamValue may contain duplicates of the same Param's value.
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// in which case the later value takes precedence. It may also contain
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// ParamValues which do not correspond to any of the passed in Params. These
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// will be ignored in Populate.
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type Source interface {
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Parse(context.Context, []Param) (context.Context, []ParamValue, error)
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}
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// ParamValues is simply a slice of ParamValue elements, which implements Parse
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// by always returning itself as-is.
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type ParamValues []ParamValue
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// Parse implements the method for the Source interface.
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func (pvs ParamValues) Parse(ctx context.Context, _ []Param) (context.Context, []ParamValue, error) {
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return ctx, pvs, nil
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}
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// Sources combines together multiple Source instances into one. It will call
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// Parse on each element individually. Values from later Sources take precedence
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// over previous ones.
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type Sources []Source
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// Parse implements the method for the Source interface.
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func (ss Sources) Parse(ctx context.Context, params []Param) (context.Context, []ParamValue, error) {
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var pvs []ParamValue
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for _, s := range ss {
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var innerPVs []ParamValue
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var err error
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if ctx, innerPVs, err = s.Parse(ctx, params); err != nil {
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return nil, nil, err
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}
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pvs = append(pvs, innerPVs...)
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}
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return ctx, pvs, nil
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}
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